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Web 2.0 Fly By Web 2.0 is really an “after-the-fact” catch-all for a collectively recognized phenomena the foaf project
Inhalt des Dokuments
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Web 2.0 is the network as platform, spanning all connected devices; Web 2.0 applications are those that make the most of the intrinsic advantages of that platform: delivering software as a continually-updated service that gets better the more people use it, consuming and remixing data from multiple sources, including individual users, while providing their own data and services in a form that allows remixing by others, creating network effects through an "architecture of participation," and going beyond the page metaphor of Web 1.0 to deliver rich user experiences. Tim O'Reilly, “Web 2.0: Compact Definition?”
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What Makes the Web 2.0 Different? • Personalized • User oriented • Easy to Use • Get you to the information you want • Useful
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Characteristics of Conventional Web Application • “Click, wait, and refresh” user interaction > Page refreshes from the server needed for all events, data submissions, and navigation > The user has to wait for the response • Synchronous “request/response” communication model • Browser always initiates the request
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Issues of Conventional Web Application • Slow response • Loss of operation context during refresh • Excessive server load and bandwidth consumption • Lack of two-way, real-time communication capability for server initiated updates These are the reasons why Rich Internet Application (RIA) technologies were born.
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Rich Internet Application (RIA) Technologies • Macromedia Flash • Java Web Start • DHTML • DHTML with IFrame • AJAX
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Macromedia Flash • Designed for playing interactive movies • Programmed with ActionScript • Implementation examples > Macromedia Flex > Laszlo suite (open source) • Pros: > Good for vector graphics • Cons: > Browser needs a Flash plug-in > ActionScript is proprietary and hard to debug
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Java Web Start • Desktop application delivered over the net • Pros > Desktop experience once loaded > Leverages Java technology to its fullest extent > Disconnected operation possible > Application can be digitally signed • Cons > Old JRE-based system do not work
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DHTML (Dynamic HTML) • DHTML = JavaScript + DOM + CSS • Used for creating interactive applications • No asynchronous communication, however > Full page refresh still required
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Introduction ◼ AJAX = Asynchronous JavaScript and XML ◼ AJAX is not a new programming language, but a technique for creating better, faster, and more interactive web applications. ◼ With AJAX, your JavaScript can communicate directly with the server, using the JavaScript XMLHttpRequest object. With this object, your JavaScript can trade data with a web server, without reloading the page. ◼ AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages. ◼ The AJAX technique makes Internet applications smaller, faster and more user-friendly.
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About AJAX ◼ AJAX is Based on Web Standards ◼ AJAX is based on the following web standards: ◼ JavaScript ◼ XML ◼ HTML ◼ CSS ◼ DOM ◼ The web standards used in AJAX are well defined, and supported by all major browsers. AJAX applications are browser and platform independent.
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DOM (Document Object Model) ◼ Object Oriented Representation for XML and HTML documents ◼ Based on Hierarchical (Tree) Structure ◼ allows programs and scripts to build documents, navigate their structure, add, modify or delete elements and content ◼ Provides a foundation for developing querying, filtering, transformation, rendering etc. applications on top of DOM implementations
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CSS (Cascading Style Sheets) ◼ Set of Formatting rules that tell the browser how to present the document ◼ Helps to separate the content from the presentation ◼ Reduce the download time by removing the formatting information from the document ◼ More control over formatting than HTML
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So why is AJAX so hot—NOW? ◼ Demand for richer applications is growing ◼ Broadband means we can—and want to—do more ◼ Recent Google applications have sparked people’s imagination ◼ Google gmail, Google suggests, Google Maps ◼ People are thinking of building APPLICATIONS…not just sites ◼ The Tipping Point ◼ All of this has made rich internet apps reach its tipping point—where adoption spreads rapidly and dramatically
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Real-Life Examples of AJAX apps ◼ • Google maps ◼ > http://maps.google.com/ ◼ • Goolgle Suggest ◼ > http://www.google.com/webhp?complete=1&hl=en ◼ • Gmail ◼ > http://gmail.com/ ◼ • ZUGGEST- an XMLHttp Experiment using Amazon ◼ > http://www.francisshanahan.com/zuggest.aspx
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